A medical X-ray CT (Computed Tomography) apparatus (an X-ray laminography apparatus) includes a bed unit on which a subject lies, a circular gantry unit which can contain the bed unit, and a console unit which includes a monitor for displaying a state of the subject. The gantry unit includes an X-ray emitting unit which emits an X-ray toward the subject and a plurality of detector packs which detect the X-ray transmitting the subject. The detector packs are disposed in parallel in a rotation direction of the gantry unit.
The detector pack includes, for example, a first substrate made of a ceramic material, an optical semiconductor element which is provided on a first main surface of the first substrate, and a scintillator which is provided on the optical semiconductor element. In addition, the detector pack includes a second substrate which is electrically connected to the first substrate through a flexible substrate, an ASIC (Application Specific Integrated Circuit) which is provided on the second substrate, and an image processing device which is provided in the second substrate. The ASIC collects an electrical signal output by the optical semiconductor element, generates an electrical signal to be used in image processing based on the electrical signal, and outputs the electrical signal to be used in the image processing. The image processing device performs the image processing based on the electrical signal output by the ASIC.
On the other hand, the detector pack is requested for suppressing noises by shortening an electrical distance between the optical semiconductor element and the ASIC. As a structure for shortening the electrical distance between the optical semiconductor element and the ASIC, there is known a structure in which the ASIC is directly provided in a second main surface of the first substrate.